…the wiki is characterized by an almost complete lack of structure, which is one reason that facilitates contributions to a wiki, and explains its success.
The thing to remember here is that a wiki starts with a lack of structure so that its users can define the structure that best serves their needs.
That’s what makes it so successful. People don’t have to learn a new structure, and fit their work into that structure, which is automatically limiting. Instead, they can focus on their work, and build a structure as they go – one that evolves with their information and doesn’t get in the way!